The association of weight for height and triceps skinfold with seven respiratory symptoms has been examined using logistic regression analysis in 7800 5 to 11 year old children (6200 in England and 1600 in Scotland). The results support the view that overweight children have a greater liability to some respiratory symptoms than other children. After allowing for age, sex, and social factors, significant (P less than 0.05) or borderline non-significant (P less than 0.1) positive associations were found between weight for height and the prevalence of bronchitis, 'chest ever wheezy', and 'colds usually going to the chest'. This suggests that some respiratory illness can be reduced by preventing children from becoming overweight. If this is correct, more than nutritional gains can be achieved by implementing an effective health education programme on obesity.